Apparatus for automatic production of music



Feb. 13, 1951 J. M. HANERT APPARATUS FOR AUTOMATIC PRODUCTION OF MUSIC11 Sheets-Sheet 3 Filed Nov. 1, 1945 Xbm Feb. 13, 1951 J. M. HANERTAPPARATUS FOR AUTOMATIC PRODUCTION OF Music Filed Nov. 1, 1945 llSheets-Sheet 4 Ill.

KWM

J. M. HANERT 2,541,051

APPARATUS FOR AUTOMATIC PRODUCTION OF MUSIC Filed Nov. 1, 1945 Feb. 13,1951 11 Sheets-Sheet 5 J. M. HANERT APPARATUS FOR AUTOMATIC PRODUCTIONOF MUSIC Feb. 13, 1951 11 Sheets-Sheet 6 Filed Nov. 1, 1945 [five/22%,John M Heme/t J. M. HANERT APPARATUS FOR AUTOMATIC PRODUCTION OF MUSICFeb. 13, 1951 11 Sheets-Sheet 8 Filed Nov. 1, 1945 11 Sheets-Sheet 9 J.M. HAN ERT Feb. 13, 1951 APPARATUS FOR AUTOMATIC PRODUCTION OF MUSICFiled Nov. 1, 1945 Ski fm ewzor ALLA- VYYVv John/1% bbrrb J. M. HANERT2,541,051

11 Sheets-Sheet 10 APPARATUS FOR AUTOMATIC PRODUCTION OF MUSIC 'IIQI.\IIQIII' Feb. 13, 1951 Filed Nov. 1, 1945 Patented Feb. 13, 1951APPARATUS FOR AUTOMATIC PRODUCTION OF MUSIC John M. Hancrt, Park Ridge,111., assig-nor 1:0 Hammondlnstrument. Company, Chicago, 111., a.corporation-of Delaware Application November 1, 1945, Serial No. 626,150

28 Claims.

Mylnvention relates generally to apparatus for production as sound or asa signal for recording purposes, without the employment of musicians inanyway whatsoever. In other words, the in" vention contemplates that'acomposeror-arranger may, using the apparatus ofthe invention, score themusical composition, whereupon the music will be producedautomaticallyby the apparatus with all the variations usually present in orchestralrenditions of music, such variations being in pitch and tone quality, involume, in accent of individual notes, in tempo, and in tone intensityenvelopes.

While some features of the invention are applicable to the control ofconventional mechanicaland electrical musical instruments, the inventionis herein illustrated as applied to the control of electronic musicalinstruments and apparatus It is thus among the objects of the inventionto provide:

1'. An apparatus whereby a suitable record marked upon paper or the likeand representing all of the character-istcs oi'tone quality, of toneintensity envelope, accent, tempo and the like may be automaticallytranslated into electrical signals representative of an orchestralrendition of a musical composition;

2. An improved means for producing a record of the musical score;

3. An improved means for controlling the output of a plurality ofelectrical musical instruments;

4. Improved means for detecting and translating a musical score markedon paper into signals utilizable for the control of musical instruments;

.5. An improved'apparatusin which one record may be used to control thepitch, accent and the like whereas another marked recordis selectivelyoperated by the first marked record to secure predetermined changes inthe instrumentation, vi 1 bratov and volume;

6. An improved apparatus for securing a multiplicity of predetermined,changes in tone quality, tone intensity envelope, accent, tempo, vi-

brato and likev by means of a single mark on the main controllingrecord;

7.. An improved record of paper or simi ar material composedof aplurality of cards overlapping in a shingle-like manner soas to form along record-in which shrinkage of the paper or iii) 2 other materialdoes not have any appreciable effect;

8. A series of overlapping tables for supporting the record wherebyleveling of the tables is facil'itated;

9. An improved notation card having imprinted thereon a set of timing orrhythm markings and. a set of note "position markings extend ingvperpendicular to. the timing or rhythm marklugs;

10. An improved scanner mechanism operating in timed sequence forsensing the musical notations marked upon the. record cards;

11. An improved scanning, mechanism. which does not injure, obliterateor otherwise render. ineffective the scored musical markings. eventhough used repeatedly;

12. An improved electrical transducer for converting the scannedmarkingsintov corresponding changes in electrical current flowing through anelectronic load circuit;

1'3. An improved alternating current generating system producing musicaltone frequencies with means for transmitting, collecting, andcontrolling the intensity envelope characteristics of the tones by adirect current determined by a scanning mechanism;

1%. An improvedlorchestral, registration and control table having meansfor moving it in response to score markings;

15. An instrumentality of the above mentioned, type in which the overallexpression in the output is control ed by markings on a record; and

1.6.. An improved record scanning mechanism in which the speed ofscanning is controlled by markings on the record being scanned.

Other objects. will appear from the following, description, referencebeing .had to the accompanying drawings in which:

Figure l is .a schematic diagram showing the relationship of the-variouscomponents of the complete apparatus;

Figures 2, 3, 4 and 5 are schematic diagrams of various forms ofscanning circuits and associated elements;

Figure 16- is aschematic diagram of the circuit employed to operate thesolenoidoi the instrumentation sequence table under the control of markngs on vtl-lerecord Figures '7 and 8 are schematic diagrams of thecircuits and associated elements of two modified tor-ms of scanningapparatus;

Figure 9 is a plan view of thetime sequence or record supportingstable;

Figure is a side elevational view of said table;

Figure 11 is an enlarged fragmentary sectional view taken on the line lI of Fig. 9 and showing one of the record card locating pins;

Figure 12 is a plan view of the instrumentation sequence table;

Figure 13 is an end elevational view taken on the line l3l3 of Fig. 12;

Figure 14 is a plan view of one of the record cards showing exemplarycontrol markings thereon;

Figure 15 is a schematic wiring diagram showing the circuits forproducing accents and for causing changes in overall volume of theoutput;

Figure 16 is a schematic circuit diagram of the coupler system and themeans for controlling the transmission of tone signals to the outputsystem;

Figure 17 is a schematic wiring diagram showing the means for producingXylophone-like tone envelopes;

Figure 18 is a schematic diagram showing the circuits and associatedelements for producing sustained tones;

Figure 19 is a schematic diagram illustrating the means for controllingthe production of percussive effects such as drums and the like;

Figure 20 is a schematic diagram showing the circuits and associatedelements for controlling tone quality;

Figure 21 is a schematic diagram showing the means for causingacceleration and deceleration of the scanning apparatus relative to therecord; and

Figure 22 is a schematic diagram showing a modification of the means forsensing card notations.

General description It is customary practice in the production oforchestral music for the composer to write the original score, possiblywith only infrequent notations as to the instrumentation to be employed,and in some instances without any instrumentation. This score is thenused as a guide by the arranger (who may also be the composer) and thescores for the various instruments of the orchestra are written, usuallya separate score for each instrument of the orchestra by which thecomposition is to be rendered. In music to be arranged for an orchestraof a large number of pieces this is a tedious process, while itnevertheless requires a high degree of artistry and skill.

Thereafter the arrangements of the musical compositions are utilized bythe members of the orchestra for rehearsal and final rendition of thecomposition. The composer ultimately usually has but slight control overthe instrumentation employed by the orchestra and it is only after thesetedious and time consuming steps have been taken and the orchestraultimately renders the composition that the com oser can actuallyaudition his composition played in the manner the public may be ex ectedto hear it.

Especially in the making of phonographic or similar sound recordingsfrequent rehearsals are necessary in order to assure that the recordingmade will accord with reasonable fidelity with the ideas of the composerand orchestra conductor as to how the composition should be interpretedand rendered. In actual practice it is seldom that a recordingrepresents the closeness to perfection which is anticipated by thecomposer and conductor, since in each rendition by an orchestra a faultor imperfection in technique by one or more of the musicians is likelyto manifest itself. In endeavoring to correct the faults of a previousrendition, the conductor is likely to find that other faults haveinsinuated themselves.

The difficulties inherent in the orchestral production of a compositionmay be compared to those which would confront an artist who found itnecessary in painting a picture to destroy the complete or partiallycomplete picture he was painting every time he became dissatisfied withany slight detail of the picture. The painter is not subject to suchstringent regulation but instead merely repaints such minor portion ofthe whole picture which does not represent the subject being paintedsufficiently accurately to meet his artistic approval. In endeavoring tomake a musical phonographic recording, the artist conductor does nothave this opportunity to erase and correct slight blemishes in detailsbut instead must rehearse the orchestra repeatedly until the completecomposition can be rendered in reasonable compliance with his artisticconcept of how the rendition should sound.

In the method and apparatus of this invention the composer, arranger, orconductor has at his command means for controlling the quality of eachnote, its intensity, intensity envelope, the degree of accent, duration,and tempo without necessarily affecting any other note or tone of thecomposition. He thus has under his control, within the limitationsimposed by the apparatus as a whole, facilities for producing, under hissole control, any of a substantially inr finite variety of renditions ofa composition.

In actual practice it has been found that it is not ordinarily practicalto provide too many separate instrumentalities for producing the tonefrequencies and controlling their various characteristics such asquality, tone intensity envelopes and the like, since in the musicultimately produced, even the most trained musician cannot detect minorchanges in these qualities of the music. Since most auditory as well asother perceptions are governed by th Weber-Fechner law that the stimulusmust increase in geometrical steps to cause noticeable difference insensation, the number of steps of gradation in volume, degree ofvibrato, change in intensity envelope, and changes in tone quality, neednot be very great.

The apparatus includes means for supporting marked notation or recordcards, comprising a long sectional table having rail along itslongitudinal edges for a motor driven scanning carriage. The recordnotation cards have suitable perforations cooperating with locating pinsprojectin upwardly from the table, the cards being laid on the table inoverlapping shingle fashion. The cards may be of any suitable size, onepractical size being approximately 11" x 12". The cards suitablemarkings indicating the measures of the music to be scored thereon, eachmeasure being divided into quarter tones, 8th tone intervals as well asmaking provision for triplets aggregating a quarter tone. In aggregatelength there are suificient cards (39) to score a composition of atleast 96 measures. For convenience there are three cards side by side toaccommodate the usual number of required varieties in orchestralcontrol. In addition, there are provided two instrumentation controlcards which are located on a separate instrumentation table andcoopcrate with a separate scanning apparatus.

In scoring a composition to be produced the composed or arranger maysuitably mark cards in aznackz'and: by'rmaztltine the-cards todndicaterhei order-.1 in. which; thev, are to; he; pla ed. up h tables,. they5may; be-.initially scored, by; the .com: poser." or: arranger; at". his;home; or; desk. The:

scoring?mayhegefiec-tediira; variety or ways; asqby marking -thecardszwith; asuitable graphitepencil to; make an. electrical conducting:mark, or; by using; a; conducting ink such. as a? quick; drying aquadegasolution... ifhe useof a pencil. has beenfound; most; practical.because: of ther-easewith through-a suitable: electrcmagneticallyoperated eseapement mechanism. Thus whenever-a major change ofinstrumentation is desired amarlrwill:

lie-placed upon the notation cards-to cause advancing ofatheinstrumentation sequence-scanner onerstepi The latter scanner is.similar to that oi the notation, scanner but= the relays operatedundenits control .efiect moreor less-overall changesin -.instrumentation. andvibrato and. the like.

Accent andoverall outputvolume may be controlledzfrom the notationcards. The output is supplied to a; monitoringspeaker; and to aphonographic or similar recorder tenths-production of a masteryrecordfrom which the usual commercial pressings or other reproductionsmayhe made.

Layoutof apparatus The overalllayout of the apparatus. best. beunderstoodhy the referenceto Fig. l in which" thecarrangement isdiagrammatically illustrated. The timesequence table 35.; hears thenotation cards. which control the operation of-thetime se quence scanner32. This scanner operates throughrelays andsolenoids tocon-trol'theoperation. of the. instrumentation sequence table 34, withitsscanner.36, as .wellas to control .the openation of directcurrent controlsystems I; II, III- andlV illustrated asbloclrs Al, 42, lit-and 44.

Furthermore, relays controlled by thescanner 32 control accent systems Ito IV illustrated inv Fig.1 as clocks El, 52. 53and, respectively. Inaddition-,..the scanner 32. controls the operation of an overallexpression control 56.

The instrumentationsequence scanner controls. the.vibrato.introducing.means 65, 62, 63 and E i respectively for the tonegenerating;systemsl.to IV shown as blocks H tolfi. In addition, an instrumentation frequencyscanner controls the operation of tone quality systems I to IV shown asblocks Site 84 and volume systems I to IV shown as blocks 9% to 94respectively in Fig. 1. Eachoi-the-tone generating systemsli to lssuppliesmusical tim si nals to. he-dir ct current.

controlsystems .415 toldd,. respectively; and the signalsfrom: thelatter-are. supplied tothetone ual-.-

itysystemsfll-to respectively; Assmodificdby" the tone qualitysystems,thesignalissunplied to the accent systems 51 to 54-, and-theoutputthereof; is. amplitude. controlled lav-the: volume system, The c utput sof; the latter. volume: ey s. terns-are. supplied-to; the expressioncontrol. appaz ratusifizand the signelfromthe latterapparatus:

The relays operate= toconnect the 3; isasupplieeh thmu hr. an. oupuirsyem 9.5.. toa res cordec 9.51 or monitoring speaker; 91 or. both, defpending uponz the: positions, or. manually operated:-switchesrtfizandfit.

Scanningapparatus;-

The notation cardswhich arepl'aced upon the timesecuence table was Wellas the instrumentation determiningcards mounted on the instrumentatio'nsequencetablo are preferablyof' the general formindicated inFig 14'. Thecard I00 shown in Fig. 14 is prov-ided with-a: locating apertnrei il land" an alignment aperture ii to main-- instrumentation sequence table.The details of themai'kings appearing on the cards tilt of Fig; lfwillibe described hereinafter out it will be noted'that the cardisprovidedwith a pluralityoi' markingstsuch: as that; thesemarkings-being of graphite, aquad'ag or si or conductingmater-ial whichmaybereadily an lied to the cards.

The scanningxapparatus shown inFig. 2 com-- prises a pair-of contactbrushes 166, which may I hev inwthe form of thin wires ofPhosphorbronzeor similar: resilientconducting 'material, and arearrangedito brush along the surfaces of thecards Hill: as the scanningapparatus moves along the time sequence table. (or as theinstrumentation sequence table moves past its scanner). Upon" passingaconducting mark 5% on a card: associated'with a pairof the contactbrushes [96; a circuit. from the positive terminal of a source of platecurrent [06 to the control grid Hii -of a pentode H2 is completed, thiscircuit including asuitable series grid. resistor R! M. When thecontacts 596 are. not in engagement with a conducting mark, the pentodeI I2 is'negativelyhiased" substantially to or beyond cutoff byconnection of thegrid' l lilto the negative terminal oi 'abias battery Ht; the connection-to the grid 1 it being through the resistor R514 and aresistorRHfi, the latter having acapaoitor Clfl'l in shunt there with;The cathode and suppressor grid of the pentode '2' are illustrated. asvconnected to ground, this being the potential of the-negativetermi nalofthe'voltage source I08 and the posi tive terminal of' the biasingvoltage source I I6. The-screen grid'of this pentocle is connected tothe=positive terminal of the plate voltage source H38.

A direct current control circuitimpedance i1 lustrate'das aresistance R!i8 is connected between the plate of the pentode H2 and the positiveterminal oithe source Hi3, while a control means 4 L44, which may or maynot include a relay (as will appear from thedescription of Figs. 6 and3), is connected across the plate load resistorRllc ofthe pentode H2.This means controls thetransmission of tonesignals from a tonegenerating-system i'! to id-to a transmission means i255, which-may heconsidered as comprising elements contained in blockaE-i-Bd; 5I54, St-At, 56. Q5 and 91. I lt wilrbe apparent froma consideration of thecircuit shownin Fig. 2 that-when contactbetweenbrushes iilfi iscompleted by engagement of conducting'marlc M on one of the recordnotation cards Hit, the grid iii) will rapidly shift positive withrespect to the cathode of thepentocl'e llZ causing a sudden flow ofplate current; The resulting dropin voltage across the impedance RI 2%provides a substantial signal impulse through. the conductor H9 whichconnects-the plate oft pentode- I i-2' with the control means tain it inproper position on the time sequence or 4I-44. As a result, the wires II9 may be long and those for the various pentodes II2 (of which thereare in the illustrated embodiment I68 in the time sequence scanner and II2 in the instrumentation frequency scanner) may be joined in a cablewithout danger of interference by inductive or capacitative couplingbetween the individual wires or of resistive leakage. The plate currentdrawn by the tube H2 is relatively constant and independent of theactual impedance at the pencil marks, being, in all cases, limited bythe series grid resistor Ri I4 to that value that just corresponds tothe initial flow of grid current.

In some instances it may be desirable to couple the contact brushes I06directly to the control means, as illustrated in Fig. 3. In this figurethe signal from a source such as 1I-14 is impressed directly across theinput circuit of a non-linear control pentode I22, the character of theinput signal being capable of being modified to some extent by closing aswitch I24 to connect a capacitor (H25 in parallel. with a capacitorCI26 and with a grid resistor RI28. The contact brushes I06 control thepotential of the cathode from a value beyond cutofi to a suitableoperating potential by connecting the cathode to a suitable negativepotential source, shown as a terminal -135 v., through an appropriatetonal envelope attack and decay network comprising capacitors CI30 andCI3I and resistors RI32 and RI33. Suitable operating potentials areapplied to the remaining electrodes of the pentode I22, the platepotential being applied through load resistor RIM. The signal. appearingacross the load resistor RIM is impressed upon the transmission meansI20.

In operation, completion of a circuit across the contact brushes I06results in increasing the cathode to screen potential on the pentode I22, thereby to cause plate current how at a rate determined by the meshCI30, CI3I, RI32, Rl33, and upon breaking the circuit between thebrushes I06 the cathode potential will increase at a rate, determinedprincipally by the values of CI30 and RI33, to a value where screen andplate current cease to flow. CI3I will ordinarily be small relative toCI35] and is provided mainly to prevent undesirably rapid transients.Thus the signal originated in the generator 1I-14 will appear in thetransmission means I20 with an intensity envelope determined by the meshRI32, RI33, CI30 and. Ciel. RI32 is of value in the order of 2 megohms,thus making the resistance of the pencil mark small in comparison. Thecathode voltage (as well as signal amplitude) is substantiallyindependent of the resistance of the pencil mark. The pentode I22 willact as a non-linear class C amplifier so that only the most positiveportions Of the signal wave impressed upon the grid will produce asignal in plate circuit. The result will be that the output signalappearing in the transmission means I20 will vary somewhat in tonequality with amplitude, as is more fully described in the patent toLaurens Hammond, No. 2,l26, l64.

A further modified form of scanning means is shown in 41. In thisembodiment of the invention the notation card is made or conductingmaterial such as a metal sheet or a composite metal foil and paper sheetin. The sheet is connected at all times to the negative terminal of thebiasing battery I I6. To make notations upon the conducting card I40,short strips I 42 of ad- 8. hesive cellulose tape, or the like, areplaced upon the sheet I46 at such points at which it is desired to havea tone signal controlling relay operate. The control grid I44 of apentode I46 is connected to a single brush !48 through grid resistorRI50. Thus the grid I44 is normally main tained at the negative biasingpotential. Whenever the brush contacts one of the insulating strips I42,this circuit to the negative bias potential is broken and a positivepotential is impressed upon the grid I44 through a resistor RI 52 whichin this circuit is in series with RI50. RI52 will normally be ofsufiiciently high value relative to RI50 that the pentode I46 will becut oiT or substantially cut off whenever the brush I48 makes contactwith the conducting notation card I40. When the brush passes over aninsulating strip I42 the grid swings positive and plate current flowsthrough winding I54 of a relay I56, the switch contacts of which mayform part of the direct current control system 4I-44. Undesirablechattering at the relay I54, due to small insulation particles or duston the conducting notation card, is prevented by the inclusion of asmall condenser CI51 connected from grid to cathode.

As a further example of the manner in which the notation cards may bemarked and the markings translated into a direct current, there is shownin Fig. 5 a capacity pickup system. In this system notation cards, suchas the card I00, are placed upon a conducting surface provided by ametal plate I60, the markings I04 on the card being likewise made byaquadag or graphite. One terminal of a source I62 of radio frequency isconnected to the metal plate I60 while the other terminal is connectedto the cathode I64 of a detector pentode I66. A single brush I68,adapted to wipe past the marks I04 and to make contact therewith, isconnected to the control grid of pentode I66 through a grid resistorRI'I0. This control grid is normally connected to a suitable negativepotential source through a resistor RIIII and a resistor RI12 in seriestherewith, the cutoir potential being suflicient to maintain the pentodeI66 cut off despite the presence of low amplitude RF signals picked upby the brush I 68 due to stray capacity effects. The output circuit ofthe pentode comprises a relay winding I14 having an RF bypass capacitorCI16 in parallel therewith. A switch I18, closed upon energization ofthe relay winding I14, may be in a direct current control circuit.

From the foregoing it will appear that the apparatus shown in Fig. 5 isadapted to close the relay switch I18 whenever the brush I68 iscapacitatively coupled to the radio frequency source I62 due to itscontact with one of the conducting marks I04, but that normally thepentode I66 is biased beyond cutoff, so that the relay I14 isdeenergized and switch I18 open.

Escapement operating circuit for instrumentation sequence table Thecircuit shown in Fig. 6 is particularly adapted for the operation of theescapement mechanism of the instrumentation sequence table, to bedescribed hereinafter. This circuit includes a pair of brushes I66adapted to make contact with the markings I04 on notation cards I00 inthe manner described with reference to Fig. 2 and thus change the gridbias on pentode I'80 from cutoff to a conducting value, therebyenergizing winding I02 of a relay having a switch I84. The lower contactI of the switch I84 is connected to ground through a relatively. largecapacitor C186 and. is connected to an operating potential'sourceindicated asv +300 v. through a relatively, high. value resistor RIBS.The other contact of the switch. IE4 is connected to one terminalof asolenoid winding let,- the other terminal of the solenoidbeing connectedto, ground.

When the brushes make contact with a mark N34,,the relay 582 isenergized to close the switch 184. It will be apparent thatthe capacitor C186 is at all timesconnected across a suit able operating potentialsource through the resistor R188. Therefore, when the switch i8 3closes, the capacitor Cl83 will discharge rapidly through the solenoidwinding l st and cause the latter to operate its-plunger. Thissolenoidmust be relatively powerful for reasons which Will-ap pearhereinafter and, if i were not for the useof the energy storingcapacitor (H86; the solenoid would impose an undueload upon anyconventional vacuum tube power supply system: By providing thiscapacitor, however, thedrain up'on the power suppl extends over anappreciable time interval and thus the amperage of thecu'rrenttdrawn isvery. low, but the energysupplied over. such a long period of time isinstantly available for energiz'ation or thissolenoidwinding E90;assuring quick and powerful action-of this solenoid'.

Ifdesired, the scanning of the notation'cards andtheinstrumentation--sequencecards may be accomplished by photoelectricmeans, as shown in Figs. land 8.

In Fig; 7 the card lilfia bearing contrasting lightintensity markingsiil lis illuminated by a neon tube i94- provided with a suitablecondenser lens system let. The neon tube is'energized by an alternatingcurrentsource i96- of suitable frequency, such for example as 200 to50010. p. s. Aphototube i98 having-a lens 'system I991 directed at theportion ofthecard illuminated by the neon tube 94; is connected acrossthe input of a detector pentod'e 2%; Either of: the lens systems I96 andI99, especially the latter, preferably includes a suitable mask sothateach of the: phototubes I98 will respond only to'markings ona particularrow of the card: I a, as the latter moves past the photo'- tube, forexample, init'ne direction indicated by the arrow. Operating potentialfor the phototube I98 is supplied from a suitable source through aresistor RZQZ and thesignal therefrom is impressed upon the controlgridot a: pentode-2ii5,through a capacitor C264 and gridv resistor R296.A potential sufficient to bias the.

pentode Zililbeyond cutoff isimpressed upomthegrid of this .pentodethrough azea inseries. with RZiiii. The output circuit. of the pentOdeZOt-rincludes a relay winding 210 in parallel with a high frequencyby-pass condenser C212.

From the foregoing description of the apparatus shown in Fig. '7, itwill appear that whenever. the phototube I98 scans a dark mark on.

the notation card iota, the intensity of the signal produced therebywill decrease suiiiciently; that the pentode 2% will be biased beyondcutofLthereby interruptingthe plate; current and; deenergizing thewinding 2m of the relay, permitting its sWitchZM-to close. When,-however, the darkmark has passed the fieldof View. of; the phototube98,- a. signal corresponding to. the

frequency of the source I93. willxbeimpressedl across the inputiiltlandf will result .in .plate. ourrentflow throughthe relaywindingfliiil: to open:

It will be, understood that: theits. switch; 21 4.-

Switch 214 will be in adirect' current control cir-' cuit and controlthe transmissionof a signal from the tone generating system to theoutput system or the instrument. To assure less inter ferencefrom'outsidelight sources, the portion of the notation card 1 56a beingscanned is preferably shielded bya= light shield 2-16;

Instead of utilizing the photoelectric scanning system to operate relaysin the direct current control ineans the signal produced by the photo--tubes in scanning markingsmail beus'ed directly to control thetransmission of the signal from the tone generating" system to theoutput sys tem, as show'n'i'n Fig. 8': l'nathis figurethe means forillumination or the card and thephotoelectric pickup is substantiallyidentical with that described with reference to Fig. '7; but the cardare preferably iso'f non-reflecting blackand has white notationmarkings; thereon. The signal from the phototube I-QEoi Fig; 8isimpressedupoii the grid of a pentode 222 through ablocking condenserC224. Suitable cutoff and* light thresholdv bias is impressed'- upontl-i'e grid of the pentode 222 through a: resistor R2 -2Bi Thusas theamplitude of the output of the phot'otube 198' increases, thealternating component of the plate current of pentode 222 willcorrespondingly increase invalue. The output or: the pentode 222' iscoupled through a. capacitor C228 with a mesh comprising arectifiercuode23cin-para1ie1 with a capacitor C232 andresistor- R234; This meshis connected to the cathode 2 36-of arnoh=linear signal control pentode2 38 through a' resistor R249; The musical tone signal "ge'rierated bya: source 2132: is impressed acrossthe input Dru-1e pentode 238, oneterminal of the generator'beingconnectedto the gridzaaz-cr thepentode-through a decoupli'n gres-is'tor R266. An audioafre'quencyby-pass capacitor GMBdsconnected in the oathode circuit while theremaining: electrodes of this pentode are connected in the usual mannerto suitable sources. of operating. potential. It

willbe seenzt-hatthe outputof the p'entod 222 is rectifiedandifilteredxandimpressed upon the cathode 236, to, cause thepentode 238 toc0'nductplate. current under: the controror the signal.impulsesuprovidedby thegenerator 242. The rate atv which the: cathode 2:36.15" drivennegativeby the alternating: signalzprodu'ced in the output of: pentode.2.22isac0ntr0l1'ed by the valuesoi thefiltering and delaying. capacitorC232" and re'sis tor R234; .ancl. tozsomei extent by the values of" RNBand GHB'. By-selecting these resistors and;

capacitors, of appropriate values; the amplitude of: the signal output.or the i pentode 238"- may be made to occur with any. desiredpredetermined tone intensity envelope uponthe'scanning of anotation markon .the card'i228.

Notatiorn'and instrumentationsequence cards Each columnis arranged to bescannedby apa'lr' There are threerows'rof brushes W6 (Fig. 2). ofnotation" cards placed side by side and two! instrumentation card'splaced side-by side;

The cards arepreferably made of a-duil finishmaterial which will readilytake pencil marks and are of several ply thickness so they'may bedurable and-ieasily'handled: The paper may be specially treated torender it less subject to shrinkage dueto changes-in humidity; and is 11preferably tested to make sure that no parts thereof are electricallyconductive.

In 14 the card is illustrated as having exemplary markings I04 thereon,the markings being indicated by cross-hatching. It will be noted thatthe columns 30! to 366 are arranged in rough simulation of a pianokeyboard in that the Ci and D# columns are "Xd while the F#,- G# and Aiicolumns have parallel line. shading. This facilitates marking all thecards by the arranger or composer. In order to avoid the necessity thatthe composer or arranger completely fill in the block markings I04, hemay merely draw a line parallel to and within the column and anassistant may thereafter fill in a complete marking represented by thecrosshatching in Fig. 14.

As illustrative of the character and scope of the instrumentationavailable, the character of the operations controlled by the variouscolumns of the notation and instrumentation cards which have been foundpractical, will be set forth.

Of the first notation card, columns 30! to 34! will be used to determinewhich of the notes C2 130.81 c. p. s.) to E5 (1318.51 0. p. s.) ofgenerating system I are to be sounded. Columns 342 to 353 of the firstcard will be used to determine which of the notes F (43.654 0. p. s.) toE! (82.407 0. p. s.) of the bass generating system II shall be sounded.Column 354 will be marked when any note of generating system I isrequired to be weakly accented. Columns 355 and 356 will be marked tocause strong accents on tones of generating system I, and medium accentson the tones produced by the generating system II, respectively.

Of thesecond notation card, columns 30! to 34! will be marked todetermine which of the notes C2 (130.81 0. p. s.) to E (1318.51 c. p.s.) of the generator system III shall be sounded. Columns 342 and 343will respectively cause weak and strong accents of the tones ofgenerator system III. Columns 344 to 356 will respectively control notesG2 (196.0 0. p. s.) to G3 (392.0 c. p. s.) of the accompanimentgenerator IV.

Columns to 34! of the third notation card will be used respectively tocontrol notes C2 (130.81 0. p. s.) to E5 (1318.51 0. p. s.) of agenerating system V. Column 342 is used to control medium accents on thenotes of accompaniment generator IV, while columns 343 and 344 areutilized respectively to control weak and strong accents on generatingsystems V. Columns 345 and 346 of the third card are used respectivelyto cause rapid and slow deceleration of th motor driving carriage toproduce decelerando eifects. Similarly, columns 341 and 34B are used toproduce slow and rapid accelerando effects. Marks in columns 349 to areutilized to produce various degrees of decrescendo effects, while marksin columns 352 and 354 are utilized to provid various degrees ofcrescendo effects. Marks in column 355 produce drum effects. A mark incolumn 356 will produce an orchestration shift, that is, a change in theinstrumentation sequence table so as to effect any desired change in theoverall instrumentation employed.

The first instrumentation card utilizes a mark in columns 30! to 304 tocontrol the output volume of generating system I. are used to determineth register of generating system I. Columns 309 to 3!3 are utilized toselect the tone quality of generating system I. Column 3!4 is used tomute the tones of generating system I, while column 3l5 is used to,

Columns 305 to 308 1 cent table.

determine whether the tones of generating sys tem I shall have vibrato.Columns 3!! to 325 control the percussion branch of generating system I,columns 3!! to 320 determining the degree of volume, while columns 32!to 325 select any on of five tone qualities for the percussion branch ofgenerating system I.

Columns 328 to 33! are used to select any one of four degrees of volumefor bass generating system II, columns 332 to 334 selecting any one ofthree registers for this generating system, and columns 335 to 339selecting the tone quality of the bass generating system I. Columns 342to 354 control the operation of generating system III, the first fourcolumns determining the volume, the next three the register, the nextfive the tone quality and column 354 controlling the vibrato.

On the second instrumentation card, marks in columns 30! to M0 controlthe output of the accompaniment generator IV, the first four columnscontrolling four different degrees of volume, the next five columns fivedifferent tone qualities, and the tenth column the vibrato. Columns 3I3to 323 are for the control of generating system V, the first fourcolumns of this group controlling different degrees of volume, the nextfive different tone qualities, while the last two respectively controlthe mute and the vibrato. Marks in columns 325 to 333 control the outputof the percussion branch of generating system V, the first fourcontrolling different degrees of volume, while the remainder controldifferent tone qualities. Columns 336 to 346 control the drum section,the first four columns determining different degrees of volume, the nextfive different tone qualities, and the last two determining differenttone intensit envelopes.

In the center of each card there are numbers 0 to 9 imprinted inalignment with transverse lines 360. The distance between these lineswill normally represent the time interval of a quarter note, thus fourtimes this distance between the lines 360 will represent a measure in4/4 time. Intermediate the lines 360 there are dash lines 362 dividingthe quarter tone interval into eighth tone intervals. There are alsolight lines 364 dividing each quarter tone interval into three equalparts for the scoring of triplets.

The notation card table As shown in Figs. 9, l0 and 11, the notationcard table is built up in sections, the first section 366 beingconstructed in the manner of a conventional table with four legs 36".The remaining table sections 368 are provided with only two legs, bothat one end of the table section, the other end of the table resting uponbrackets 310 projecting from the adjacent legs of the adja- Suitableshims 312 are provided so as to make the tables 368 level with oneanother.

A pair of tracks 314, preferably of inverted T-' section, are secured tothe tables by suitable brackets 376 and successive sections thereof arebolted together by suitable fish plates 318. By virtue of thisarrangement, the tables may quickly and easily be assembled with thetracks smooth and level.

The locating pins for positioning the notation cards upon the tables arepreferably of the construction shown in Fig. 11. From this figure itwill be seen that each of the pins is mounted in the table top 31'!projecting through an enlarged hole 380 formed in the top. Each pin 382has a reduced diameter rounded end portion 384 for engagement in the.-perforations of. the cardS,. and has. a washer 385rwelded thereto. Thelower end of; the. pin. is. threaded for a clamping nut 3.88 which bearsagainst; awashei: 389, aqsuitable lock washerc'sil'being. utilized. Thewashers 3-86 and 389 are of .suihciently great diameter that. uponloosening. the nut 388., the pin .3.82. may be moved in. any directionwithin the. limits of the hole 384;. thereby facilitating accurate.location of the ends 384 of the pins. in the table? with. the tolerancescustomary in woodworking: practice and after the rails 314 have beensecured to the tables and all of the tables are assembled, the ends 334:or the: pins may be accurately located with. reference. to: the pins in:adjacent tables so that. their. spacing may he accurate to a high degreeof precision.

The scanning carriage The'scanning carriage, designated generally by thereference character 2W2, is mounted upon V- grooved or flanged wheels393 resting on the tracks 314- and is driven by a motor 394- through asuitable speed reducing gearing which is enclosed in the motor housing.Suitably mounted on the carriage are 168' pairs of brushes Hlwhichproject downwardly a-t'an angle so as. to resiliently contact the threecards placed side by side uponthe surface of the table. Most of theelements of the circuit shown in Fig. 2, such as the pentodes H2 andcircuit elements EH4, RH5- and RI l8 and Cl H, are alsocarried bythecarriage.

The conductors i i-9 from the fifty-six pen-todes H2, as well asconductors supplying operating potential for these pen-todes are boundin a flexible cable 396 leading" to the other components of theapparatus.

The instrumentation sequence table The instrumentation sequence table isshown in Figs. 12 and 13 as comprising a base4'0ll having a pair ofV-grooved rails 4E2 mounted thereon for the reception of ball. bearings40.4. A movable table 406 has corresponding grooved rails 408 which restupon the balls. 454,, thus providing an anti-friction support forlongitudnial movement of the table 496- relati-ve to the base 400.Suitable locating and aligning pins 382-, 384 are provided for properlypositioning a pair of cards I00 (Fig.14) upon the table 496.

Along the center of the table are tworows of staggered upwardlyprojecting pins M0 for cooperation with an escapement pawl 412 which issuitably pivoted on a cross frame 414 and operated by a solenoid I98.The table 406 is drawn rearwardly by a long tension spring 4i8 which hasits end respectively anchored to the base 400 and a pin 420 projectingdownwardly from the table 406. The cross frame 414 is guided forvertical movement in a. pair of grooved posts 422 projecting upwardlyfrom the base 400. The cross frame carries two banks of contact brushesI06, there being 56 pairs of contact brushes H16 in each bank. Thesecontact brushes cooperate with the markings on the cardsv lflil tocomplete circuits and cause energization of relays in a manner such asdisclosed in Figs. 2, 4 or 5.

Thus when there is a conducting mark in column 356 of the third notationcard, the contact brushes I06 making contact therewith will render thetube I83 (Fig. 6) conducting, energizing the plate circuit relay I82,I84 and permitting the charge stored in the capacitor (N86 to energizethe solenoid. I90. Whenever the solenoid 1-90 The holes380. may bedrilled through resistors R443, R449 and R450.

signals of the various generating systems.

The system as a whole is preferably rendered more flexible in use byproviding means whereby the connections of the conductors us (Fig. 2)maybe selectively coupled to any of the various control means. In thisway there may be as many tone generatingsystems as desired and onlythose selected for the rendition of a particular composition may becoupled to the instrumentation sequence scanner.

Expression control and volume system The expression control indicated bythe block 56 in Fig. 1' and the volume control systems represented bythe blocks 9i to 9:2 of Fig". l are preferably of the nature shown inFig. 15.

In the latter figure the output systems of seven generators arediagrammatically illustrated, these output systems corresponding to theoutputs of the'tone quality systems 8i to 34 of Fig. 1', each beingillustrated as being coupled by a transformer having a secondary winding436) to the input of a preamplifier tricde 432 through meshes comprisingresistors R433 to R438 in series and shunt resistors R439 and R440. Eachof the resistances R433 to R43! is shunted by a switch 44'! operated bya relay 449a, these relays being operated by the scanning brushes usewhen they contact appropriate markings on the notation cards of the timesequence scanning system.

The resistors R433 and R435 are of properly graded values so that uponenergization of the relays associated with resistors R433 and R434difierent degrees of accent will be produced by changing the impedanceof the mesh, which includes these resistors, for the particulargenerating system upon which the accented note is desired. Likewise theresistors R435, R436 and R431 are preferably of such values that uponsuccessive operation of the relays 45m associated therewith the volumemay be increased and decreased logarithmically. The shunt resistors R440of the various outputs of the generating systems are connected in seriesbetween ground and the decoupling resistor R4558 so as to mix thesignals of the various generating systems.

' The amplitude of the combined signal of all the generating systems hasits amplitude controlled by decrescendo relays 44th, 542 and 4-43 andcrescendo relays 444, 445 and 4%. The relays 441* to 443- uponenergization are adapted to connect the control grid of the preamplifiertri ode 432 to a grounded conductor 4 3? respectively These resistorsare of graded values so that upon successively energizing the relays443, 442 and 44lb the amplitude of the combined signal appearing on thegrid 432 will be decreased in logarithmic steps. On the other hand, theenergization of the relays 444, 445- and 4 16 will result in openingcircuits through resistors R455, R452 and R453 so as. successively andin a logarithmic manner increase the effective resistance between thegrid. of triode. 4,32. and the grounded conductor 441. In this manneroverall crescendo and decrescendo eifects may readily be obtained byappropriate markings in the six columns or the notation card.

The output of the preamplifier triode 432 is coupled to a poweramplifier 454 (forming part of the output system 95-Fig. 1) and suppliedto the monitoring speaker 91, or the recorder 96, or both.

Octave coupler system As shown in Fig. it, suitable controls arepreferably provided in the apparatus for effecting octave coupling sothat by the provision of a single mark upon the notation card the outputsignals of a number of octavely related generators of a particularsystem may be simultaneously coupled to the output of the apparatus as awhole. in Fig. 16 there are five pairs of scanning contact brushes 106which are representative of the brushes cooperable with two or threeoctaves of markings for a particular generating system. Each pair ofbrushes operates through a pentode such as H2 (Fig. 1) to control arelay, these relays bearin the reference characters 468, 46!, 462, 463and 464 respectively. These relays, upon energization, are adapted toconnect a source of suitable operating potential, indicated as +210 v.,to bus conductors 416, 41!, 412, 413 and 414 respectively. A pluralityof octave coupler control relays 415, 416, 411 and 418 (Fig. 16) areadapted to be energized by appropriate markings upon the instrumentationsequence cards, and respectively control the addition of the secondoctave, the octave, the unison, and the suboctave. Each of the relays415 to 418 has a plurality of switches 419, one associated with each ofthe bus conductors 416 to 414, so as to connect the latter through ahigh value decoupling resistor R488 to the input or" one of theplurality of suitably biased rectifier pentodes tit-2. Connectionsbetween the resistors and the rectifier tubes 482 are such that when therelay 411 s energized and a relay such as 4th is energized, only thenote represented by the marking which has resulted by the energizationof relay 466 will be sounded, whereas if in addition the relay 416 isenergized, the note and its octave will be sounded, since in this casethe bus ile will be connected through two decouplin resistors R489 todifferent rectifier pentodes 482 as will hereinafter appear. This willresult in sounding of the note and its octave.

Each of the rectifier pentodes 462 has a relay 484 in its outputcircuit, this relay being adapted upon energization to connect asuitable potential shown as l35 v. to the cathode of a control pentode480 through a circuit identical with that shown in 3 and operating inthe same manner to cause the transmission of a signal from a tonegenerator 1 [-14 to its output system represented by a signal collectorconductor 488.

Since in Fig. 16 only a representative portion of a complete octavecoupler system is disclosed, the generators 'ii Hi will generateoctavely related frequencies such as those of the notes Ci to C6, Whilethe relays 4613 to 26 5 Will be respectively associated with the contactbrushes 106 of the card columns representing octavely re lated notes C2to C6.

The resistors R463 are of high value relative to the input impedances ofthe pentodes 42. Thus when two or more of the relays 415 to 418 areenergized at the same time, no spurious circuits can be completedbecause the resistors R488, being of high value (with respect to thegrid-to -cathode resistance when the grid is drawing current) preventsubstantial current fiow in a reverse direction. For example, if therelays 411 and 418 were energized and the note controlling relay 460onergized the first and second pentodes 482 (from the top) would have anoperating potential impressed upon their grids, suihcient to cause gridcurrent flow and thus to reduce their input resistances from infinity toa value low in comparison with R486. Thus, this enormous drop in inputimpedance prohibits a substantial current .to flow from the gridconductor of the second pentode 482 through its associated resistor R480to the conductor 41!. It will be apparent that if there were anyappreciable flow through said last named resistor R486 to the conductor4, current might also flow to the grid of the third pentode and energizethe latter. However, as each of the pentodes 482 is rendered conductingand at very low input impedance by impressing the high grid voltage(+216 v.) on its grid circuit through R486, there is sufiicientgrid-to-cathode current flow in the pentode so that the actual potentialof the grid is very low and, therefore, there cannot be a sufiicientpotential buildup upon grids of other pentodes 42 through the previouslydescribed spurious paths to cause the latter to conduct current.

In Fig. 16 it is assumed that the generator system is of limited gamut,extending through the note C5 but not extending to the note C1. As acompromise result, the switches connected to bus conductor 414 andassociated with the relays 415, 416 and 411 and the resistors R480connected thereto are in parallel and connected to control he generatorfor the note C6.

The generating system employed with the octave coupler control system ofFig. 16 is preferably of the type shown in the patents to L. HammondNos. 2,126,464 and,2,126,682. It will be noted that the method of signalamplitude control which includes the pentode 486 of Fig. 16 is similarin principle to that disclosed in said Patent No. 2,126,464.

Xylophone tone signal generating system It is nearly a practicalnecessity for the artistic rendition of orchestral music that percussivetones be employed to provide contrast to the sustained tones and,therefore, means for producing percussive tones of the Xylophone type,as shown in Fig. 17, is provided. In Fig. 17 contact brushes I 06 areadapted, through the pentode l I 2, to control the operation of a relay490, which upon energization connects a negative potential source,indicated as v., through a mesh, comprising resistors R491, R492, R493and R494, to a terminal 495 of the tone quality system 84. The resistorR492 has a capacitor C496 in parallel therewith and the junction betweenthe resistors R493 and R494 isconnected to ground through a resonantmesh comprising an inductance L491 and a capacitor C498. A controlpentode 499, which corresponds to one of the pentodes 486 (Fig. 16) isadapted to control the output of a suitable signal generator 11-14, theoutput of the pentode 499 being suitably coupled to a tone qualitysystem 8l94. The terminal 495 represents a common terminal for aplurality of the meshes R45 to R494, C496, C498 and L491 associated withother relays similar to relay 490.

The frequency generated by the particular tone generator 1|14 associatedwith the pentode 489 is preferably the same as'that at which the meshL491, C498 is resonant. Upon energization of 17 "the-relay-MBthetransient-produced upon; closure its 1 switch 7 is transmitted to theterminal "495 through the intervening mesh, but only suchifr quencies ascorrespond rather closely to 'frequencies of the generator II-M will betrans-- mitted to the outputsystem. The resonant mesh L491, C498 *doesnot have a su-fliciently high Q to exclude lrequencies'difieringby'asmuchzas a semitone or morefrom the output and therefore this signal isheard as a percussive musical-tone of recognizable-but=not'--a-solearly-"define'd -in pitch as the usual sustained type oftone.

Upon closure of the switch of relay 4 53 the negative 135 v. potentialisimpressed uponthe cathodeof the pentede 49-9, through t'he resistor R49!and additional attack resistor RS'iiEl, ata rate determined inpart loycapacitor C591; there- "by rendering the-pentode 499 conductive-"of't-hesignal supplied'by the generator 'll-74. After 'deenergization of the=re'lay 450; cathode current is still supplied to theepentode 499 fromthecapacitor 0501, so that the tone willdecay at a :gr-adual ratedetermined by the relative values-or R550 and C595. 'Thus uponenergization-of'the relay A9 0 a: signal :constitu-ting l bothapercussiwtone and asustained tone ('thelatterbeingproducedbythe-generator' 'lk lfl of rapid attack and slightly-slower decay, will be produced in :the :output -system. This tone-.-will be respective- :lynf thexylophone and brass types and-williuseful inimany orchestral renditions.

Generator system jjQTi'fIMTQZLSSiUfi piano-like tones -In"Fig.l8th'ere"is"illustrated acircuit suitable for the control of the toneenvelope of a.gen- J ierator system iprcducing sustain-ed tones, under'theco-ntrol'of "conducting 'markings on a'notation card. In thiscircuit contact "brushes I do, upon passing 'over "a conducting mark onthe card. change the grid f-bias of a'pentode 582 from negative-valuebeyond "cutoitto a positive value in a manner similar to that previouslydescribed with reference to Fig. 3. ;In :Fig. 18, however, the pentodeB2 operates as an impedance changer 'so that thevalue o ftheresistanceiinposed by the markingjon'the card across the 'brush'eslllfiis notof controlling character. This is"bec,ause"th'e peritode 5'62decouples the card 'mark and "cable impedances from the. remainder ofthe circuitwhi'chis of high impedance -would be susceptible to spuriousleakage, etc. The anode 'ofthefperitode "502 is supplied from "a:suitable source 'ofiplatevoltajgethrough aresistor'R5fl4 in parallelwith a capacitor 105%. The anode of the .pentode 202 is also connectedto the cathode "5118 of a control .pentoide 5E0 through a resistance'R5l2. The .pentode h! has a sharp peak wave impressed thereon ,by agenerator 'H-l4 and the output of the pentode is suitablycouple'd 'toasignal collector conduc- .tor .514 throug'ha capacitor C515 and adecouplingresistor R5l8. The anodes of a, ,p1uraiity ofjpentodesSlilmay'beconnected to thecollector conductor 5 M through the same,capacitor C5 i ii and resistor R518.

When the contact brushes I96 pass over a control marking onfa notationcard, the ,pentode 502' is rendered conducting so that .the potential of"its plate drops at a rate determined by the tube characteristicsand thevalues of'CEBG, and "R584. This drop in platepotential'is reflected onthe cathodefi'UB of the .pentoder5llland therefore renders thejlatterconductive of the signal impressed upon itsinput circuit. 'It will-"henoted that the plate of pentode "502 is normally at a 53 9 and 53thereof through --'a timeconstant capacitor G532 and resistor R534.--Pla-te potential "is provided jpotential or? volts above thatofthefcathodetilti dueto the provision of abatteryfi Hi. This latter'potentialnormally completely cuts'off plate. cur- "rent in tube 5 i=0.

The circuit of Fig. 18 is of advantage'oversome of the previouslydescribed control circuits in that no electromagnetic relay is required.

Apparatus "for producing-drum signals An important elementof orchestralmusic,-.par-

ticularly that .of popular nature, is imparted by the percussion beat-of drums. I have therefore provided :a means for electronicallyproducing electrical signals corresponding to the beats-Inf drums. Such.an apparatus? is .shown in Fig. (19

as comprising the random .frequency generator 520. This generator may beany suitable source of random noise -such,- for examplewa signal pickedup from the phonograph record of the noise of waves --breaking L 'on abeach, but is-preferably an The output of i the random frequencygenerator 526 is connectedto'the-primary of a transformer pr-isingresi-stor-s R524, R525 in series and a shunt mes-h comprising R526 andG521. *Aflo'ad resistor R528 is connected in parallel with-"the primaryW-indingof a transformer 522. These'c- "ondaryof the transformer 522 hasa center 'tap connected to a 'suitable biasing -.potential--soureeindicated as-a 7 terminal :7 v.- and has its terminzils-connec-tedto thegrids'of apair of 'push-pull pentodesES-ll, 531. The screens of thepentodes are connected to the cathodes "from a source indicated as a+300 v. terminal through load-resistors R536 and R531 as wellas throughthe center tap primary "of "an output transformer The-screen grids ofthe pento'des 53!) and 53 I are nor-mally 'maintainei'l "at ground "orcathode --potential 'loy virtue of th'e'ir connection to thecathodes'ofthese-tubes-by-the resistor-R534. When the contact brushesto'ii' for 546 is energized to'connect the screen -grids 0f thepentOdes-"SBQJESI to a suitable source-0'1 operating potential shown-asa +100 v. terminal,

this .connection being effected through a-nattack resistor RMB. Two -.ormore capacitors C543,

ground. upon closure of switches 545, 5616- respectively. When bothswitches 555 and 5 19319 open,

the screen gridsof the pentodes 53i), *53l-will be rapidly-raised tooperating potential when "the relay 5% is "energizedgandthus produce apercussion tone with a very sharp attack. Wnen=-' it is desired tolessen the sharpness of this attack and to prolongthe'decay period-orthepercussion ,drum tone, either switch.545, or switch r546 or both, willbe closed, (thereby slowing up the rate 'pled to one of'tone qualitysystems '8! to 8'4, and

